A novel extracellular membrane elaborated by a mouse embryonal carcinoma-derived cell line

An extracellular membranous structure is synthesized by an embryonal carcinoma-derived cell line, M1536-B3, in suspension cultures. Analysis of the solubilized membranous structure on polyacrylamide gels in sodium dodecyl sulfate yielded two major classes of glycoproteins with molecular weights of approximately 230,000 and 320,000 respectively. The amino acid composition of the purified membranous structures revealed the absence of both hydroxyproline and hydroxylysine. Carbohydrate analysis demonstrated the presence of fucose, xylose, mannose, galactose, glucose, N-acetylglucosamine, N-acetylgalactosamine, and N-acetylneuraminic acid. These carbohydrates represented approximately 9% of the weight of the membrane. A comparison of the electrophoretic patterns of cells grown on monolayers and in suspension revealed a marked accumulation of the glycoproteins under the latter growth conditions. $\text{D}$-[³H]-glucosamine was incorporated into these two and a third major glycoprotein by cells in suspension culture.